Boiler safety device



March 29, 1960 E. M. PETERSON 2,930,866

BOILER SAFETY DEVICE Filed April 25, 1957 2 Sheets-Sheet 1 March 29, 1960 E. M. PETERSON 2,930,866

BOILER SAFETY DEVICE 2 Sheets-Sheet 2 Filed April 25, 1957 flz eza 21 @ar f gjersoz.

y will deliver heat to the boiler.

circulate due to empty or dry radiators.

United States Patent ,0 l

2,930,866 BOILER SAFETY DEVICE Edgar M. Peterson, Clarendon Hills, 11]., assignor to Crane Co., Chicago, 111., a corporation of Illinois Application April 25, 1957, Serial No. 655,023 3 Claims. (Cl. 200-81) This invention relates generally to a boiler safety device, and, more particularly, it is concerned with a type of apparatus in which electrical switches are pressure actuated to perform the safety function hereinafter described.

In order to acquire a better understanding of the need filled by this invention, it is necessary to appreciate at the outset that in connection with closed pressure vessels, such as a hot water heatingboiler, for example, there are dangers'involved from two sources; the first danger arises from a drop in pressure due to a leak in the heat ing system in which case water may slowly drain from the system until the radiators are empty. Thermostats within the house will in the normal course of their functioning call for heat to be supplied and the firing device, such as a gas burner, an oil burner, or a stoker, However, water cannot The heat delivered to the boiler will then produce steam and the fluid pressure within the system will rise rapidly to a pressure such as of the order of thirty pounds per square inch at which pressure the normally set relief valve will open, the relief valve may or may not reduce pressure to a low value and the high limit control, such as the thermostat in the upper part of the boiler, may or may not sense an over-temperature and shut off the firing device electrically. In such a dangerous situation for rea,

sons hereinafter explained, the device of this invention will open a switch concurrently with the relief valve at the thirty pounds per square inch pressureand will positively shut off the firing device electrically.

It should be clear that a low position system leak will also cause a dangerous condition to exist even if the events above described do not occur, because in many cases the Water linewill eventually drop below the level of the crown sheet of the boiler and when the firing device next delivers heat, the boiler will break due to thermal shock. Excessive temperatures can thus lead to a fire in either situation as referred to above and in such situation, this invention as hereinafter described prevents operation of the firing device long before the low water line occurs.

From the standpoint of considering overpressure arising within the system due to a failure of the firing device to shut off, this condition may occur due to a leak in the system or due to failure of other electrical controls to shut off the firing device. My invention will prevent the firing device from operating even if the pressure does rise to thirty pounds per square inch for any reason and will prevent the firing device from being reinstated until the release means of my invention is manually actuated.

It is therefore an important object of my inventionto provide not only for a drop in pressure'due to leak in the system, but also for overpressure or excesspressiiredue to the failure of the boiler firing device to shut off. It is well known that single controls exist which could perform this function, but they do not lock out on safety and they are expensive and are frequently 2,930,866 P tent dMar. 29, 1960 unable to be adapted easily or conveniently to existing installations.

It is therefore one of the more important objects of this invention to provide for a relatively simple boiler safety device which accomplishes its purpose by positively opening an electrical circuit if the boiler pressure drops below a set point as for example five to'fifteen pounds per square inch, and it will positively open the same electrical circuit if the pressure should rise to a fixed pressure point of the order of twenty-eight to thirty pounds per square inch and also concurrently with opening the electrical circuit lock the said switch in the open position until it is subsequently released'and preferably manually so that determination of the cause of the pressure rise can be made before resetting the atfected switch for normal operation.

Another important object is to provide for a boiler safety device in which a bellows or other pressure actuated member coupled with suitable linkage will translate linear movement into angular movement within a conveniently installed compact case or package.

Another object is to provide for a boiler safety de vice which is comparatively simple and relatively inexpensive to make and preferably employs known and tested elements, such as electrical switches, linkage mechanisms, bellows, and the like. I

Other objects and advantages of the structure will become more readily apparent upon proceeding with the following description read in light of the accompanying drawings, in which Fig. l is an open case or sectional view of a preferred embodiment in which the device of my invention is shown in a normal operating position.

Fig. 2 is a section taken on the line 22 of Fig. 1.

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 1.

Fig. 4 is a view similar to Fig. 1, except that the device is shown in the position indicating its response to an objectionable low fluid pressure condition within the system.

Fig. 5 is a view similar to that described in connection with Fig. 4, except that the device is illustrated in the position when confronted with excess or overpressure in the system.

Referring now to Fig. l, a conventional pressure vessel such as a heating boiler is generally designated B in which its upper surface is provided with the usual boss 1 having connected thereto a short length of pipe 2 communicating with the interior of the boiler. Preferably on the said pipe for purpose of support, a threaded bushing 3 is adjustably mounted to hold the case 4 securely in position on the boiler.

Within the case 4, which is shown with the cover C removed (the cover being shown in place in Figs. 2 and 3), a conventional corrugated bellows 5 is mounted which is hollow and expandable in the usual manner in response to fluctuations of pressure conditions within the boiler, since the boiler interior is connected by means of the said pipe with the interior of the bellows.

At its upper end, the bellows has suitably attached a vertically extending lever coupling 6 pivotally attached to the lever 7 at 10. At the upper end limit of the lever 7, as at 10a, a second pivotal connection is made thereon with the side arm 8, the latter arm being rigidly connected vertically to extending lower and upper lever portions '9 and 11 respectively. The lever portion 9,

3 may vary depending upon the nature and range of th service requirements for'which the safetydevice is intended.

At one end limit of the horizontal lever portion 12, a

guide plate Mic-preferably attachedsecurelyto the said as for example, a conventional electrical mercury switch- 19'with the usual electrical wire connections within, as

illustrated.

At the opposite endof thehorizontal lever portion 13, a vertically extending-lever 21 with a lower cuived portion, as shown, is pivotally mounted as at 22 to theend portion of the lever 13. Similarly, and in the manner described in connection with the lever 18, the lever 21 supportsa second electrical mercury switch 23. The switches 19and 23 are connected in series to a suitable electrical power line as indicated diagrammatically by the lines 24, so that if one of the switches is opened the electrical circuit is broken, thereby causing the firing.

device, such-as the oil burner, gas burner, or stoker, to be disconnected and thus'rendered inoperative. This condition will occur whether the bellows d is retracted, as shown in the low pressurecondition referred'to in connection withFig. 4, or whether the bellows is expanded as shown in the overpressure condition illustrated in Fig.

However, in the event that an overpressure condition is encountered in the course ofpressure vessel operation, it has been found desirable to employ a safety catch or detent which will retain the mercury switch 23 in its open position once this position is reached and to hold it in said open position untilmanually released,

as will hereinafter become more readily apparent.

As shown in Fig. 4, the lever- 13' is provided with a coil spring 25 attached to the vertically extending and pivotally mounted lever 21 as indicated at 26 thus normally holding the said lever in the position shown in solid lines in Fig. l. The method of attachment and the arrangement of-the release is more clearly shown in i Fig. 3, in which inplansoctional view a pivotally mounted hook 27 has a coil spring 28 positioned between the inner wall of the case 4 and the back of the hook as shown. A pushbutton 29 having an outer extending head 36 projecting through the casing C moves the said hook pivotally upon depressing the head 3%, the actuating handle 29 being slidable movable axiallywith relation to the cover C within. which it is mounted. An integral boss 31 serves to connect the hook 27 pivotally as at 32 to an end wall of the case 4.

The hook 27 is providedwith the engaging head 33 and is pivotally attached to the actuating handle 29 by means of'the pin 34.

In operation, it will be apparent that when the bellows 5 reaches the, expanded position shown in Fig. 5, because of excess pressure within the boiler, the combined tree-like leverage means is; moved on the pivotal connection Zllto the position shown. The vertically extending rod 21- willmove-past the head- 33 of the hook and thus be retained insuch position by the said hook head.

It will oi course be understood that it is necessary to correct orremove-theconditionoriginally responsible for the excess:pressureconditionbefore the hock27 is manu-.

ally actuated to allow the pivotal. lever 21 to movebackto. the normal operating position. shown in Fig. 1.

inues. hema e- 19W heleye ega orassumc aesnses illustrated in Fig. 5. It will also be appreciated that the manual operation ofthe disengaging pin 29--is* desirable here because by virtue of such type and location of the actuation it will be convenient and become more readily apparent to the operator in charge that the initial bad condition causing the excess fluid pressure within the system must be corrected before the manual release is finally set or effective.

It will be clear that, as the; mercury levels within the respective mercury switches 19 and 23 aremoved and tipped from oneend of the switch to the other, the electrical connections are accordingly made and broken, thereby to control theo erationof thefuel burner.

In further considering the operation of this safety device, it will be apparent that the mercury switch 19 set, for example, at a pressure below ten pounds per square inch will open while the switch 23 remains in the closed position. Similarly, where a high fluid pressure condition is encountered, as shown inthe leverageposition ofv Fig. 5', ifwe assume a pressure condition of the order of'thirty pounds per square inch, the switch 19 in relation to its electrical connection at 24 is closed, while the mercury switch 23 under such condition opens and is then held by means of the hook member 27 in its open position until it is manually actuated and released as hereinabove described. It will also be apparent that because of the number of pivotalconnections, as, for example, t. 0.1%, s ll as .0, nd. h s fe y e ce. posse sd si able flexi i ty h r sp t t nst l on.

under vari'edconditions. Thus, if'the boiler should; leak andpressure drop'tos ay ten pounds per square inch, the

low pressure switch19 will open and the primary control for the burner (not'shown) attached to the lines tothe electrical connections 24 will stop the firing device immediately. When the fiuidpressure within the system is increased, as, for example, when the boiler leak is re.

paired or. water is added to the boiler, the control will return. to the normal operating position shown in Fig, 1 Similarly, as boiler pressure increases, say to twenty-. e t po nds per square inch. for y re n, h high pressure switch 23 because of expansion of the bellows Swill be. opened andrwill be in theelectrically openop sition by the hook 27 until it is manually released.

It will, or" course, be understood that only a single pref: ferredembodiment ofthe device has been illustrated and described and therefore, the true scope of the invention should be interpreted in light of the appendedfilaims.

I claim:

l, Ina system for effecting safety in the operation ofa closed pressurevessel, pressure-actuated means in communication with the intcrior of said vessel, the said pressure-actuated means having enclosed flexible portions thereofreciprocally movable in response to fluid pressure fluctuations within. the closedvessel, integral lever means extending. ina plurality of substantially vertical and horizontal planes connected with said latter. reciprocally movable portions of the pressure-actuated means, a pair of mercury switchcsoppositely disposed on ends of the lever means cooperating with said latter means and pivotally. movable with the latter means and. pivotally operable means for retaining at least one of the mercury switch means in a disconnected position upon predetermined. movement of, said pressure actuated means, switchsupporting, lever means, an arcuately slotted guide member mou te noneend p rt n -fthe lever-m c pera e ingwith one, of said switchsupporting lever means, the said slotted guidemeans selectively adjusting the position of thesaid switch means relative to the said integral. lever means.

2. In. a system for; efiecting'satety inthe operation of a closedpressure vessel, pressureeactuatedmeans income municationwitlrihe interior of said vessel, the Siid;Prje,-. s re-a u t dmea s. hav ng nclo ed fl xibl rad ans. her o e ip c y mevahle n-re nc Q-flu dnressnre fluctuations ithia he dined. sel... integ al. e er} means.

extending in a plurality of substantially vertical and horizontal planes pivotally movable as a unit and connected with said latter reciprocally movable portions of the pressure-actuated means, the said latter means of connection consistingof one of the integral lever means extending normally in a lower horizontal plane and a substantially vertical lever connected to an end portion of said latter lever means extending in the lower horizontal plane, the said vertical lever being connected to an upper portion of the said pressure actuated means, a plurality of mercury switches oppositely disposed on ends of the lever means cooperating with said latter means and being pivotally movable with the latter means, pivotally operable means for retaining at least one of the mercury switch means in a disconnected position upon predetermined movement of said pressure actuated means, switch supporting lever means, an arcuately slotted guide member mounted on one end portion of the lever means cooperating with one of said switch supporting lever means, the said slotted guide means selectively adjusting the po sition of the said switch means relative to the said integral lever means.

3. In a system for effecting safety in the operation of a closed pressure vessel, pressure-actuated means in communication with the interior of said vessel, the said pressure-actuated means having enclosed flexible portions thereof reciprocally movable in response to fluid pressure fluctuations within the closed vessel, a plurality of integrally connected lever means extending in a plurality of substantially vertical and horizontal planes and being connected with said latter reciprocally movable portions of the pressure actuated means, mercury switches oppositely disposed relative to each other on ends of the lever means cooperating with said latter lever means and being pivotally movable with the latter lever means and pivotally operable means for retaining at least one of the mercury switch means in a disconnected position upon predetermined movement of said pressure actuated means, switch supporting lever means, an arcuately slotted guide member mounted on an end portion of the upper one of the horizontal lever means to cooperate with a vertical lever comprising a portion of said switch supporting lever means, the said slotted guide means having means for engaging said vertical lever to selectively adjust the position of the said switch support means relative to the said integral lever means.

References Cited in the file of this patent UNITED STATES PATENTS 971,776 Myers Oct. 14, 1910 1,651,630 Phelan Dec. 6, 1927 1,667,056 Smith Apr. 24, 1928 1,762,219 Faber June 10, 1930 1,854,519 McDonnell et al Apr. 19, 1932 1,960,856 Stacey May 29, 1934 2,088,491 Smith July 27, 1937 2,144,587 Kronmiller Ian. 17, 1939 2,283,374 Kronmiller May 19, 1942 2,298,795 Judson Oct. 13, 1942 2,357,878 Crew Sept. 12, 1944 2,473,845 Barsun June 21, 1949 2,663,498 Copping Dec. 22, 1953 2,773,957 Davis Dec. 11, 1956 2,784,271 Burch Mar. 5, 1957 

